1. The Field of the Invention
The present invention is generally related to optical devices used in fiber optic communications systems. More particularly, the present invention provides for dual stage modular optical devices.
2. The Relevant Technology
Fiber optic technology is increasingly employed as a method by which information can be reliably transmitted via a communications network. Networks employing fiber optic technology are known as optical communications networks, and are marked by high bandwidth and reliable, high-speed data transmission.
Optical communications networks employ optical transceivers in transmitting information via the network from a transmission node to a reception node. Generally, such optical transceivers implement both data signal transmission and reception capabilities. For example, a transmitter portion of a transceiver is configured to convert an incoming electrical data signal into an optical data signal and a receiver portion of the transceiver is configured to convert an incoming optical data signal into an electrical data signal.
More particularly, an optical transceiver at the transmission node receives an electrical data signal from a network device, such as a computer, and converts the electrical data signal to a modulated optical data signal using an optical transmitter such as a laser. The optical data signal can then be transmitted in a fiber optic cable via the optical communications network to a reception node of the network. At the reception node, the optical data signal is received at another optical transceiver that uses a photodetector, such as a photodiode, to convert the received optical data signal back into an electrical data signal. The electrical data signal is then forwarded to a host device, such as a computer, for processing.
Generally, multiple components are designed to accomplish different aspects of these functions. For example, an optical transceiver can include one or more optical subassemblies (“OSA”) such as a transmit optical subassembly (“TOSA”), and a receive optical subassembly (“ROSA”). Typically, each OSA is created as a separate physical entity, such as a hermetically sealed cylinder that includes one or more optical sending or receiving components, as well as electrical circuitry for handling and converting between optical and electrical signals. Within the optical transceiver, each OSA generally includes electrical connections to various additional components such as a transceiver substrate, sometimes embodied in the form of a printed circuit board (“PCB”). OSAs in a conventional transceiver are generally oriented such that a longitudinal axis defined by the OSA is substantially parallel to the transceiver substrate. The transceiver substrate, in turn, is mounted to the board of a host bus adapter (“HBA”) or other component.
The transceiver substrate can include multiple other active circuitry components particularly designed to drive or handle electrical signals sent to or returning from one or more of the OSAs. Accordingly, such a transceiver substrate will usually include a number of electrical transmission lines with the one or more OSAs. Such connections may include “send” and “receive” data transmission lines for each OSA, one or more power transmission lines for each OSA, and one or more diagnostic data transmission lines for each OSA. These transmission lines are connected between the transceiver substrate and the OSA using different types of electrical connectors, examples of which include an electrical flex circuit, a direct mounting connection between conductive metallic pins extending from the OSA and solder points on the PCB, and a plug connection that extends from the PCB and mounts into electrical extensions from an OSA.
As part of ongoing efforts to uniformly reduce the size of optical transceivers and other components, manufacturing standards such as the small form factor (“SFF”), small form factor pluggable (“SFP”), and 10 gigabit small form factor pluggable (“XFP”) standards have been developed. Nonetheless, the size of most optical transceivers, even those that comply with such manufacturing standards, best suits them for external connections to a computer system, such as a desktop computer, a laptop computer, or a handheld digital device.
For example, an SFF or SFP optical transceiver can be used to provide an interface between an optical cable and a standard network cable, such as an Ethernet cable for example, that plugs into a computer system. Alternatively, a number of optical transceivers can be mounted in a network panel and configured to include an external connection to a computer system. However, the number of components within a conventional transceiver, as well as the orientation and the size of SFF or SFP optical transceivers, makes it difficult, if not impossible, to integrate conventional optical transceivers into smaller spaces, such as within a pluggable card for use in a laptop computer or hand held device. For example, despite their relatively compact nature, conventional SFF, SFP, and XFP optical transceiver bodies are still too wide and/or tall to fit within a typical PCMCIA laptop envelope.
A related problem concerns the connections of the optical transceiver. In particular, use of the optical transceiver as an external, rather than internal, component necessitates the use of additional connectors and connections, which increase both the overall cost associated with the system as well as the complexity of the system. As well, optical transceivers employed in an external, rather than integrated, configuration are more prone to rough handling and damage than an integrated component.
Furthermore, even if the conventional optical transceiver could fit within such an envelope, the length of the conventional optical transceiver SFF, SFP, or XFP optical transceiver is such that the transceiver substrate takes up an inordinate amount of board space on a corresponding host bus adapter (“HBA”) or other component to which the optical transceiver is attached. This problem is of particular concern in light of the concurrent demands for increases in functionality and decreases in component size. These, and other, considerations make conventional optical transceivers less than ideal for integration within many computer systems. Accordingly, what would be advantageous are reduced cost optical transceivers that can fit within relatively small envelopes such that the optical transceiver can be integrated within compact components and various computing systems and devices.